CLARKSBURG, Md. (WJZ) — There’s shock and sadness over the discovery of William McQuain’s body, as prosecutors focus on the surveillance video that will be key evidence against his stepfather.

Mike Hellgren investigates several new developments.

According to new published reports, Curtis Lopez had taken a trip to Ocean City with his estranged wife, Jane McQuain. The two began arguing. She told a friend she was scared for her life.

Two days later, police believe Lopez killed McQuain in her home, and then murdered her 11-year-old son William, his stepson, and dumped the boy in the woods near Interstate 270 in Montgomery County, where dog teams found him Tuesday after an exhaustive search.

WJZ has now learned detectives used Lopez’s cell phone signal to track his whereabouts.

Family friend Charles Barnes made the cross that’s now the cornerstone for a larger memorial at the scene.

“We know what has happened to William and that he can be with his mother,” Barnes said. “When we have a service we can have them both together, hopefully. Not have this hanging over our head—worrying, waiting, looking and not having an answer.”

Flowers and pictures line the memorial to McQuain, along with notes and gifts from his classmates.

“William was the greatest, most beautiful, wonderful child in the entire world. In the entire world. There is no reason this should ever happen to him,” said Tamera Seonarian, William’s former coach.

“Who could do this to William? He’s just a little kid. Who could do this to some kid? Who could do it?” said Blake Seonarian, William’s friend.

Police say they uncovered video of William and his stepdad at a nearby storage shed just hours before they say the sixth- grader was murdered. They say William was playing, unaware of the horror that was about to come. They found more footage of him at a gas station, one that’s close to where they found his body.

“It did not appear there was any distress between the two in the footage,” said Chief Tom Manger, Montgomery County Police. “He appeared to be running around as you would expect a boy that age to do.”

Lopez has a violent past. He’s headed back to Maryland to face murder charges for Jane McQuain. Police say charges are pending for the murder of young William.

Police say Lopez has refused to cooperate with them. They say he has refused to answer any questions about what happened to William McQuain. They say they will charge Lopez with McQuain’s murder once he is back in Maryland.

Lopez was convicted of attempted murder in 1987 after stabbing a man in Pennsylvania.